1 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics A Survey of (Mostly) Current Optical and Infrared Interferometers Tom Armstrong US Naval Research Laboratory Navy Prototype Optical Interferometer (NPOI) December 4, 2006

2 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Michelson’s 20-foot interferometer, Mt. Wilson, California (used mostly in 1921)

3 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics CHARA NPOI Keck SUSI PTI VLTI Keck

4 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics LocationAperturesBaselinesWavelengths VLTI Cerro Paranal, Chile 3 x 1.8 m 4 x 8.2 m 30 to 202 m 25 to 85 m 10 μm, 5 μm, 2 μm bands CHARA Mt. Wilson, California, USA6 x 1 m35 to 300 m2 μm band NPOI Anderson Mesa, Arizona, USA6 x 12 cm5 to 80 m450 – 850 nm PTI Mt. Palomar, California, USA3 x 12 cm70 m, 100 m2 μm band Keck Interferometer Mauna Kea, Hawai`i, USA2 x 10 m70 m 10 μm, 5 μm, 2 μm bands SUSI Narrabri, New South Wales, Australia 2 x 12 cm5 to 600 m450 – 900 nm ISI Mt. Wilson, California, USA3 x 1.65 m5 to 80 m10 μm band MIRA-I (under development) Tokyo, Japan2 x 25 cmTo 30 mVisual band Interferometers currently in operation

5 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Notes VLTI Multiple backends. Largest telescope apertures in Southern Hemisphere. Adaptive optics. CHARA FLUOR fiber beam combiner. NPOI Two arrays: Wide-angle astrometry; Imaging. 35 cm and 1.4 m apertures in near future (3 years?) PTI Dual-star feed. Keck Interferometer Largest telescope apertures in Northern Hemisphere. Aperture masking also available. Outrigger array (1.8 m telescopes) cancelled. SUSI Longest baselines. ISI Heterodyne detection. Interferometers currently in operation

6 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics LocationAperturesBaselinesWavelengths MROI (under design) Magdalena Ridge, New Mexico, USA 4 to 10 x 1.5 mTo 500 m2 μm, visual bands LBT (under development) Mt. Graham, Arizona, USA 2 x 8 m 14 m center-to-center 22 m edge-to-edge 2 μm band `OHANA (under development) Mauna Kea, Hawai`i, USA 5: 4 m to 10 mTo 800 m2 μm band Interferometers under development LocationAperturesBaselinesWavelengths IOTA (closed July ’06) Mt. Hopkins, Arizona, USA 3 x 40 cm5 to 38 m2 μm band COAST (MROI testbed after ’06) Cambridge, UK5 x 40 cm3 to 100 m500 – 800 nm GI2T (closed June ’06) Obs. Côte d’Azur, France 2 x 1 mTo 50 m2 μm, visual bands Recently closed interferometers

7 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Notes MROI (under design) Goal is ~ 100 AGNs. LBT (under development) Two telescopes on a single mount (no need for delay lines). `OHANA (under development) Fibers link existing telescopes. First fringes attained in ’06. Interferometers under development Notes IOTA (closed July ’06) First use of fiber beam combiner. COAST (MROI testbed after ’06) First image using closure phase. GI2T (closed June ’06) High spectral resolution backend. Recently closed interferometers

8 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics GI2T, Observatoire de la Côte d’Azur Photo: Peter Lawson 2 x 1 m To 50 m baselines 2 μm, visual bands High spectral resolution

9 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics 3 x 0.40 m 5 m to 38 m baselines 2 μm band Fiber beam combination IOTA, Mt. Hopkins, Arizona

10 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics 5 x 0.40 m 3 m to 100m baselines 500—800 nm band First closure phase image COAST, Cambridge, England

11 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics 3 x 1.65 m apertures 5 to 80 m baselines 12 μm band Heterodyne detection ISI, Mt. Wilson, California

12 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Palomar Testbed Interferometer (PTI), Mt. Palomar, California 3 x 0.18 m apertures 70, 100 m baselines 2 μm band Dual-star feed for small-angle astrometry

13 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics SUSI, Narrabri, Australia Photo: Karina Hall 2 x 0.12 m apertures 5 to 80 m baselines 450—900 μm band Longest baselines

14 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Navy Prototype Optical Interferometer (NPOI), Anderson Mesa, Arizona 6 x 0.12 m apertures 5 to 80 m baselines 450—850 nm band Astrometry and imaging Largest number of apertures

15 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics 3 x 1.8 m apertures 30 to 202 m baselines and 4 x 8.2 m apertures 25 to 85 m baselines 2 μm, 5 μm,10 μm band Multiple backends Largest S. hemisphere apertures Adaptive optics VLTI, Cerro Paranal, Chile

16 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Keck Interferometer, Mauna Kea, Hawai`i 2 x 10 m apertures 70 m baseline 2 μm, 5 μm, 12 μm band Largest N. hemisphere apertures Also aperture masking

17 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Mt. Wilson, California: 100-inch & 60-inch telescopes, solar towers—and CHARA 6 x 1 m apertures 35 to 330 m baselines 2 μm band FLUOR fiber beam combiner Longest baseline

18 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Mauna Kea, Hawai`i 5 apertures, 4 to 10 m To 800 m baselines 2 μm band Fiber combination

19 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics 2 x 8 m apertures 14 m baseline center-to-center 22 m baseline edge-to-edge 2 μm band Two telescopes on single mount Large Binocular Telescope, Mt. Graham, Arizona

20 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics 4 to 10 x 1.4 m apertures To 500 m baselines 2 μm, visual bands Rapid imaging Magdalena Ridge Observatory, New Mexico

21 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Sample results: Cepheid pulsations (PTI) Diameter of η Aquilae vs. pulsation phase. Crosses: diameters from PTI Line: diameter inferred from infrared surface brightness method. Combining change in angular diameter (interferometry) with change in physical diameter (radial-velocity data) yields the distance. Lane et al Astrophys. J.

22 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Sample results: Cepheid pulsations (VLTI) Diameter of ℓ Carinae vs. pulsation phase. Circles: diameters from VLTI with VINCI Line: diameter inferred from infrared surface brightness method. Predicted angular diameters from infrared surface brightness methods are in good agreement with measured diameters, giving confidence in the conversion from radial velocities to physical diameter variations. Kervella et al Astron. Astrophys.

23 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics RESULTS: Vega is rotating at 93% of breakup velocity. Its equator is distended by 25% and is 2400° K cooler than the pole. We see it nearly pole-on. Vega is the major photometric standard, but model atmospheres do not fit the spectrum. IMAGE: Off-center bright polar cap shows rotation axis is tilted ~5° from the line of sight. Pole-to-equator temperature contrast (2400° K) may explain spectral anomalies. Low secondary maximum shows significant limb darkening. 22 0 2 22 2 0 RA offset (mas) Dec offset (mas) Wavelength (  m) |V 1 V 2 V 3 | Phase anomalies indicate slight asymmetry. Wavelength (  m) Closure phase (deg) Peterson et al., Nature, 2006 DATA: Sample results: Vega is a rapid rotator (NPOI)

24 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Sample results: High-precision binary astrometry (PTI) Lane 2005 PTI Position differences between components in right ascension and declination (crosses), with 1-σ error ellipses. Orbital motion is from south to north ΔRA (arcsec) ΔDec (arcsec) HD

25 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Sample results: High-precision binary astrometry (PTI) Lane 2005 PTI The goal is to detect perturbations in the orbit of a binary component due to an unseen companion (possibly a planet). Typical formal error ellipse is 5 x 100 micro- arcseconds. Fit to linear trend yields an implied repeatability of ~ 15 x 300 micro-arcseconds. Position differences between components in right ascension and declination (crosses), with 1-σ error ellipses. Orbital motion is from south to north ΔRA (arcsec) ΔDec (arcsec) HD

26 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Sample results: Polarimetric interferometry with SUSI Visibility vs. baseline length for R Carinae with SUSI at λ900 nm Ireland et al. 2005, Monthly Notices R. A. S., 361, 337 Outflow model Uniform stellar disk (no circumstellar dust) R Carinae is a Mira, a pulsating late-type giant surrounded by dust. Light reflected by the dust is polarized. SUSI data fit a model with a thin shell of dust better than a model with a thicker shell created by steady outflow. Visibility difference between polarizationsVisibility for both polarizations ,02 Δ Visibility ,0 Visibility Baseline (m) Baseline (m) Pulsation phase 0.08 Thin-shell model Note the visibility precision: ± 1.5% to 2%

27 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Sample results: Rotational distortion of Alderamin (α Cep) with CHARA van Belle et al. 2006, Astrophys. J., 637, 494 Rotational velocity: 280 km/s (83% of breakup velocity) T eff = 8440 K (poles) to 7600 K (equator) Temperature contrast implies that the photosphere is convective. Projected baseline lengths: 250 m to 312 m 2.15 μm wavelength, 0.30 μm bandwidth

28 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Boden et al. 2005, ApJ, 635, 442 HD B: Double-lined spectroscopic binary, member of a four-star system. Pre-main-sequence stars. Combine Keck Interferometer data with radial-velocity data and Hubble Fine Guidance Sensor data to find: M = 0.70 M sun and 0.58 M sun. Masses and luminosities do not fit models. Effective temperature Luminosity (Lsun) Solar metallicitySub-solar metallicity Siess et al. (2000) models Baraffe et al. (1998) models Sample results: Low-mass pre-main- sequence stars with the Keck Interferometer

29 Survey of the World’s Optical / IR Interferometers Fourth Advanced Chilean School of Astrophysics Monnier et al Astrophys. J. Sample result: Colliding-wind binary WR 98 with Keck aperture masking Image Model